This invention relates to frangible connectors, and more particularly, it relates to a frangible connector insert assembly, for frangibly connecting opposed members such as portions of a self-closing breakaway valve assembly, wherein the tension load and bending load required to separate the parts of the frangible connector insert assembly are independently selectable.
Self-closing breakaway valve assemblies are described in U.S. Pat. No. 3,921,656. The self-closing breakaway valve assemblies are particularly useful in the fuel lines of vehicles, such as aircraft and specifically helicopters. The self-closing breakaway valve assemblies provide a predetermined break point in the fuel line in the event of a vehicle crash, and seal off the fuel line after separating to prevent the escape of fuel from the fuel line, which creates an unacceptable fire hazard.
In the self-closing breakaway valve assemblies of U.S. Pat. No. 3,921,656, two rotatable valve assemblies are respectively mounted in two valve housings comprising an overall valve body. The two valve housings are held together by frangible rivets. The two rotatable valve members are spring biased to close, and trigger means are interposed between the two rotatable valve members to hold them open until a load is applied which breaks the frangible rivets and separates the two valve housings releasing the trigger means and permitting the rotatable valve members to close.
The frangible structure of that assembly has an inherent disadvantage in that its separation in response to bending and tension loads is interdependent, and the separation from a bending load occurs much more readily than separation from a tension load. More particularly, if a bending load is applied to the self-closing breakaway valve assembly, the breaking of only some of the frangible rivets on one side of the valve body permits sufficient separation of the valve housings to release the trigger means and permit the rotatable valve members to close. However, if a tension load is applied along the axis of the valve body, the tension load is distributed substantially evenly over all the frangible rivets, and therefore a high load is required to achieve separation of the valve housings. Also, the valve body could be damaged by the load such that it could not be reassembled, and in any event, it is difficult to replace the frangible rivets quickly to effect field repairs of the self-closing breakaway valve assemblies.
Improved frangible means connecting the two valve housings of the valve body are clearly required.